Historically, alkaline detergents have been used extensively to clean articles in dish machines. Alkaline detergents have been used because of their ability to remove and emulsify fatty, oily, hydrophobic soils. However, alkaline detergents have several disadvantages. For example, alkaline detergents etch glass. Mild etching has an iridescent appearance much like oil on water whereas more severe etching leaves a permanent, opaque, film-like appearance to the glass. Alkaline detergents also leave an actual film on glass. This is caused in part by using alkaline detergents in combination with certain water types, and water temperatures. While etching on glass is permanent, several solutions have been developed to solve the problems associated with the generation of hard water films. For example, rinse aids help to remove films caused by hard water. Softening the water is another way to prevent the formation of films. However, the need for rinse aids and water softeners increases the cost associated with alkaline detergents.
The co-pending PCT patent application PCT/EP02/05964 assigned to Ecolab Inc. discloses, in part, the use of acidic detergents to remove starch, where the use of an acidic detergent is followed by an alkaline detergent.
A need exists for methods and detergents that can effectively remove soils, especially hydrophobic soils, without creating the disadvantages alkaline detergents create and without the addition of extra steps like rinse aids, water softening, and two step detergent systems.